1. Field of the Invention
The invention relates to the field of ultrasound imaging. More specifically, the invention relates to three-dimensional imaging of flow structures using ultrasound imaging techniques.
2. Background Information
Various techniques and systems may be used to obtain images of the interior of a body and/or flow structures within a body. (A body is used herein to refer to various types of subjects, such humans, animals, non-living structures, etc., while flow structure as used herein may refer to a region of fluid flow such as occurring in veins, arteries, etc.)
To detect and display flow structures in three-dimensional views, several data acquisition and imaging techniques may be utilized, such as magnetic resonance imaging (MRI), CT, and ultrasound. In some applications, it is particularly useful to view the flow lumen, which usually, but not always, corresponds to the "hollow" interior cavity of a flow structure in a body. For example, imaging of flow lumen may be desired to view irregular regions that may be present in the interior of the flow structure, e.g., intimal defects, plaque, stenosis, etc., which may occur on the interior wall of an artery, vein, or other vessel. To view the flow lumen, MRI, CT, and contrast X-ray angiography imaging techniques have typically been used . However, the ionizing radiation of X-ray and CT and the substantial expense and inconvenience associated with MRI and CT equipment may often limit the use of such systems.
Ultrasound imaging techniques, on the other hand, typically provide substantially greater convenience and cost efficiency, to both the equipment operator and the subject (body), compared to the X-ray, MRI and CT imaging techniques. Ultrasound techniques that facilitate three-dimensional imaging of flow structures within a body generally involve the following steps: (1) detecting a flow structure using Doppler signals, wherein a predetermined power/amplitude/magnitude and/or frequency/velocity Doppler threshold is used to distinguish a flow region (e.g., a flow structure) from a non-flow region; (2) collecting power and/or frequency Doppler data at a number of sample volumes and/or planes (or "slices") of the flow structure; and (3) consolidating the data for the various sample volumes and/or slices of the flow structure to generate a three-dimensional, solid image of the flow structure (i.e., an image having the interior of the flow structure completely filled up; free from cavities, such that the flow lumen is not depicted from the inside of the flow structure).
However, ultrasound techniques generally do not provide the quality and accuracy of images as obtained from relatively more complex/expensive imaging techniques, such as X-ray, MRI and CT. Furthermore, previous ultrasound imaging techniques were typically limited to generating solid 3D images of flow structures. Unfortunately, solid 3D images of flow structures, as produced by past ultrasound techniques, have been unable to depict desired images of the flow lumen, such as, for example, the interior wall, including irregularities, of an artery, vein, or other vessel.